Process for detecting unauthorized introduction of any data transmitted by a transmitter to a receiver

Abstract

The process is intended to establish whether the data transmitted by the transmitter (SE) to the receiver (EM) have been tapped and spuriously reintroduced at a later point in time and/or have been inadmissibly altered. For this purpose, the signature (S) assigned to the useful data (D) is enciphered symmetrically, using a combination of coupling data (K), characterizing the coupling between transmitter and receiver, and random data (Z), generated by a random generator. The coupling data are transmitted in plain text, the random data are enciphered. On the receiver side it can be established whether the transmitted message has been tapped and reintroduced at a later point in time if the coupling data are inadmissible. An alteration of the transmitted message can be established from ascertaining that the key used for enciphering the signature, obtained from the combination of coupling data and random data with the aid of a one-way function, does not correspond to the key obtained during deciphering at the receiver and consequently the deciphering of the enciphered signature leads to an incorrect result. The incorrect signature is detected during verification of the signature.

We claim: 
     
       1. A process for detecting unauthorized reintroduction of any data transmitted by a transmitter to a receiver, the process comprising the steps of: developing a signature from the data in the transmitter,   symmetrically encrypting the signature in the transmitter using a key which is dependent on coupling data designating a transmission between the transmitter and the receiver, including: generating random data in the transmitter,   establishing the coupling data,   generating a symmetric key by one-way enciphering of a combination of random data and coupling data in the transmitter,   enciphering the signature with an aid of the key in the transmitter,   enciphering the random data with a transfer key in the transmitter,     transmitting a message comprising the useful data, the enciphered signature, the coupling data and the enciphered random data from the transmitter to the receiver,   checking the message to determine if errors are present in the message, and rejecting the useful data if errors are present.   
     
     
       2. A process as claimed in claim 1, wherein said coupling data are dependent on a time of transmission of the data. 
     
     
       3. A process as claimed in claim 1, further comprising the step of: transmitting the coupling data in plain text to the receiver.   
     
     
       4. A process as claimed in claim 1, wherein the step of checking the message further comprises the steps of: checking the coupling data on a receiver side and, if there is a discrepancy, rejecting the message,   recovering the random data by deciphering with the transfer key the enciphered random data,   determining the symmetric key by one-way enciphering of a combination of the calculated random data and coupling data,   recovering the signature by deciphering the enciphered signature with the aid of the calculated key,   checking the signature and, rejecting the message if errors are detected.   
     
     
       5. A process as claimed in claim 1, further comprising the step of: using a symmetric key as the transfer key.   
     
     
       6. A process as claimed in claim 1, further comprising the step of: using an asymmetric key as the transfer key, proceeding on a basis of the public-key method.   
     
     
       7. A process as claimed in claim 1, further comprising the step of: replacing the signature by a check sum of the useful data.   
     
     
       8. A process as claimed in claim 1, wherein said coupling data are dependent on the receiver. 
     
     
       9. A process as claimed in claim 1, further comprising the step of: influencing the key at the transmitter by pseudo-random data.   
     
     
       10. A process for detecting unauthorized reintroduction of any data transmitted by a transmitter to a receiver, comprising the steps of: developing a signature from protocol data wherein the data are protocol data;   symmetrically enciphering the signature using a key which is dependent on coupling data designating the transmission between the transmitter and the receiver, including: generating random data in the transmitter,   establishing the coupling data,   generating a symmetric key by one-way enciphering of a combination of random data and coupling data in the transmitter,   enciphering the signature with an aid of the key in the transmitter,   enciphering the random data with a transfer key in the transmitter, and     transmitting a message including the data and the signature to the receiver, and   checking the message and rejecting the message if errors are present.   
     
     
       11. A process for detecting unauthorized reintroduction of any data transmitted by a transmitter to a receiver, comprising the steps of: developing a signature from a combination of protocol data and useful data;   symmetrically enciphering the signature using a key which is dependent on coupling data designating the transmission between the transmitter and the receiver, including: generating random data in the transmitter,   establishing the coupling data,   generating a symmetric key by one-way enciphering of a combination of random data and coupling data in the transmitter,   enciphering the signature with an aid of the key in the transmitter,   enciphering the random data with a transfer key in the transmitter, and     transmitting a message including the data and the signature to the receiver, and   checking the message and rejecting the message if errors are present.